Infections may speed Alzheimer's memory loss

A split-view image showing PET scans of a normal brain (L) and a brain with Alzheimer's disease. REUTERS/National Institute on Aging/Handout

Catching a cold or the flu could speed memory loss in people with Alzheimer's disease, researchers reported Tuesday.

In a study of patients with mild to severe Alzheimer's disease, they found that people who suffered acute or chronic infections, or even bumps and bruises from a fall, were much more likely to have high blood levels of a protein involved in inflammation and also experienced faster memory loss than people who did not have infections and who had low levels of this protein.

It's possible that finding a way to reduce inflammation in the body could be beneficial for people with Alzheimer's disease, study chief Dr. Clive Holmes, from the University of Southampton, UK, said in a prepared statement.

Over about 6 months, Holmes and colleagues measured the cognitive abilities and blood levels the inflammatory protein TNF-alpha of 222 people with Alzheimer's disease. They also interviewed each subject's main caregiver several times during the study.

During follow up, roughly half of the study subjects experienced a sudden infection or injury that led to inflammation, and a spike in TNF-alpha levels. These people, the researchers found, experienced memory loss that was at twice the rate of those who did not have infections or injuries.

People who had high levels of TNF-alpha in their blood at the beginning of the study, a sign of chronic, ongoing inflammation, had memory loss at four times the rate of those with low levels of the protein at the start of the study.

By contrast, subjects with low levels of TNF-alpha throughout the study showed no decline in brain function, the report indicates.

One might guess that people with a more rapid rate of cognitive decline are more susceptible to infections or injury, but we found no evidence to suggest that people with more severe dementia were more likely to have infections or injuries at the beginning of the study, Holmes noted in a prepared statement.